The present invention relates generally to the textile art, and more particularly to a textile machine, and to a method of operating the same.
Still more particularly, the present invention relates to a method of exchanging full bobbins for empty ones in an open-end spinning machine, and to an apparatus for carrying out the method.
In many textile machines, yarn is wound onto a bobbin which is usually in form of a cylindrical or conical tube. When the bobbin is full, that is when it has a so-called "yarn package" formed thereon, the winding of further yarn onto it must of course be terminated. This is done, and thereupon the full bobbin is removed from the take-up station at which it has been rotated to wind yarn onto it, and an empty bobbin is put in its place. With the ever increasing speed at which modern equipment of this type operates, and with economic considerations dictating the efficiency requirements which are made of such machines, it is of course in most instances not practical to rely upon manual removal of the full bobbin and its replacement with an empty one, at least not usually. The art has therefore developed automatic devices for exchanging full bobbins for empty ones. Many of these devices are quite successfully used, for instance with yarn spooling machines wherein the yarn supply to the winding mechanism will be stopped immediately after the winding operation has been interrupted. As a rule, these prior-art devices are constructed as units which travel along the respective machine, and are provided with a mechanism which withdraws the full bobbin from the bobbin-driving drum, and with a mechanism which supplies an empty bobbin from a magazine.
The basic principle of operation of many of these devices of the prior art is that the yarn withdrawal is interrupted when the winding-up of yarn onto the full bobbin is terminated, and remains interrupted until the empty bobbin is mounted in the machine and the free yarn end which was created by severing the yarn from the package of yarn on the full bobbin, has been connected with the empty bobbin.
However, there are many instances where these prior-art devices are not suitable for use. For example, open-end spinning machines produce yarn in a continuous flow and unless the yarn will be continuously taken up, that is will be taken up without interruption, the yarn being produced will become entangled and will have to be discarded. In these machines, in which it is not possible to interrupt the taking-up operation so that the same must continue even as the full bobbin is replaced with an empty one, the prior-art automatic bobbin changing equipment cannot be utilized.
A proposal has been made in the prior art to provide such a piece of equipment which can be used even with open-end spinning machines and similar textile machines wherein yarn is supplied continuously and at a constant rate. This prior-art proposal utilizes severing means for severing the yarn between the full bobbin and the spinning unit from which the yarn is continuously derived. On the other hand, a negative-pressure mechanism is provided which, during the bobbin changing operation, continuously draws off the yarn being supplied by the spinning unit and carries it away. This continues until the yarn is engaged by a newly installed empty bobbin and winding of the yarn onto this empty bobbin commences. That amount of yarn which has been drawn off by the negative-pressure mechanism during the time at which winding onto the previous full bobbin was interrupted and at which winding onto the new empty bobbin has commenced, is severed and is discarded as waste material. Since obviously the production of large amounts of waste material represent an economic loss, it is desired that the waste yarn length be kept as short as possible. Evidently, for this reason it is desirable that the bobbin change period also be kept as brief as possible, particularly if high spinning speeds are concerned, that is if the yarn is being produced at a high rate of speed and continuously must be withdrawn as waste material until winding onto a new empty bobbin can commence. However, the speed of bobbin exchange is limited in this prior-art device because the empty bobbin is not supplied until the full bobbin has been withdrawn from its position at the take-up station. Once the empty bobbin has been supplied, it is installed at the take-up station by being forced on a bobbin-driving drum and only now will be empty bobbin begin to rotate and come up to speed. Evidently, during all this time period, yarn which is continuously being produced by the spinning until will go to waste as it is drawn off by the negative-pressure mechanism. Aside from this drawback, this prior-art device mentioned above does not provide for the formation of yarn reserve on the empty bobbin, which is also disadvantageous.
The industry is, therefore, still searching for an approach to the problem of exchanging a full bobbin for an empty one in a textile machine in which yarn is being supplied continuously to the take-up station.